heres a own all build get boots 3 pots go to lane get Q first max W it does the most dmg Q doesnt scale as well get 2 dorans blades first back and ninja tabi/merctreads after that get bruitilizer max E last also get bloodthirster than lastwhisper
get blackcleaver than sell dorans blades and build a frozen mallet and a maw yoru done

~boots(turn to ninja tabi or merc treads if your losing lane/ boots of ionia if you arent having issues)/pots,
~rush warmogs, then brutalizer(build this into black cleaver),
~depending who you are top against(ap or ad) build armor/magic resist(like randuins omen or maw of malmortius which end game would both be great to have)
~bloodthirster
~spirit visage(i would build this after black cleaver) or guardian angel(this would be last) work as well.
level 1- Q
level 2- E
level 3- W
Max Q first, then E, then W(as its always a .75sec "stun"), level R when possible

You can use E or Q as an initiator, but when you get to them use your W to stop them. if your ult is up, activate it before going in as it gives you extra damage. Since your abilities "charge" your blade for a little extra damage, I play her as follows:
R,E,W,Q,autoattack,Q,autoattack,Q,autoattack,R again for the finisher(more damage the lower health they are)

A question for you both: I found that in s3 boots+3 is not viable at all for my main, Rumble. I have movement speed quints, so my base speed is usually above 350, so I usually get 9 pots + wards. It's helped me in a lot of ranked games for early dominance.

Other than that, I usually get brutalizer first, then go BT. You both say it's better to first get more defensive stuff?

should pretty much always max her e first, q last. Both e and w get lower cooldowns with higher ranks, but this isn't the case for broken wings. The utility it offers early on makes it a lvl 1 skill, but that utility doesn't scale with level.

um idk how new you are but AA between every Q is huge. a good harrass strat is e in AA w AA Q away. unless you max Q which alot of people do then its e AA Q AA W AA Q AA Q AA. but all her combos are flexible which is why shes fun.

been playing her since release (not so much anymore) whilst this gives you more dps you can spam all your Qs and still get the passive proc afterwards without wasting any through them timing out, if you AA inbetween each skill it takes age to complete a combo and riven is a very bursty character (R E W QQQ R pretty much kills anything with a full stacked BT without auto attacks inbetween)

i mean you only get three stacks not the cd on her passive but i also find my self not doing the q aa q aa, its all situational on riven which is why shes so fun, what you max, how you combo, is all different.